Whipworms are intestinal parasites seen in dogs. Whipworms cause diarrhea and blood in feces as well as weight loss, lethargy, and even death in severe cases. Diagnosis is made by performing regular micro-scopic fecal examinations. Treatment consists of oral medications. Some heartworm preventatives assist in prevention. Re-infestation may occur due to contact with areas contaminated with feces (dirt, runs, cages, etc).